The present invention relates to a method of impregnating a resin of uniform thickness onto a web using a floating blade, in particular, to a method of continuous impregnating process to obtain a web having a resin of uniform thickness despite impregnating conditions.
U.S. Pat. No. 3,526,536 discloses a bead coating process of a web and the apparatus thereof. In this prior art, a knife-like control means is employed in controlling the uniformity and flatness of the coated film. However, the concept of a floating knife has not been employed as a means to accommodate variation in liquid height, and this will cause undesirable effect to the uniformity and quality of coating. As a result, it will not be suitable for semi-batch or batch system. In addition, the concept of floatation and the balance of force have not been used to self-adjust the gap between the web and the floating knife so as to mitigate the factors (vibration of the solution surface, speed change of the web, etc.) which cause the changing of the coating uniformity and quality.
U.S. Pat. No. 4,500,584 to Frank J. Modic discloses a roofing fabric membrane structure and the manufacturing method thereof. In this process a base coating composition is applied to a base fabric material and then the coating composition is cured.
U.S. Pat. No. 4,543,145 to Peter Schnell et al discloses a process for the continuous production of single-ply or multiply laminates. The process comprises applying a continuous resin film onto a travelling web, carrying the resin film being combined with a pre-tensioned web and curing the resin carrying web thus formed.
In both the prior patents, U.S. Pat. Nos. 4,500,584, and 4,543,145, a fixed knife or air knife is used to remove the excess of the resin to control the thickness of the resin are disclosed. These prior art do not disclose the employment of the balance of the surface tension force and hydrodynamic force in order to lower the influences of thickness due to the variation of impregnating conditions. If these influences are to be reduced, other supplementary automatic control equipment or devices must be added. For instance, in U.S. Pat. No. 3,526,536 to A.C.Spengos et al disclosed a method and apparatus applying a liquid to the surface of a web by the dip coating and bead coating processes. Other prior methods have been disclosed on the removal of the excess of resin coated on the web. For instance, by doctoring with air knife, blade or knife. However, the doctoring devices are firmly fixed in position from which constant doctoring force is maintained magnetically on either side of the web. In such a case, if the impregnating conditions change, the gap between the web and the floating bar will not change accordingly.